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      <title>非阻塞I/O模型 - 交互式测验</title>
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          border-radius: 8px;
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          margin-bottom: 12px;
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        .option-item:hover {
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        .option-item.selected {
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        .quiz-footer {
          padding: 20px 30px;
          display: flex;
          justify-content: space-between; /* 将按钮分布在两侧 */
          align-items: center;
          min-height: 65px; /* Reserve space */
        }

        .nav-btn {
          background-color: #4a90e2;
          color: white;
          border: none;
          border-radius: 8px;
          padding: 10px 20px;
          font-size: 16px;
          font-weight: 500;
          cursor: pointer;
          transition: background-color 0.2s ease, transform 0.2s ease;
          box-shadow: 0 4px 12px rgba(0,0,0,0.15);
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        .nav-btn:hover {
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        .result-box {
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            display: flex;
            justify-content: center;
            gap: 20px;
            margin-bottom: 40px;
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        .score-card {
            background-color: #f8f9fa;
            border-radius: 12px;
            padding: 20px;
            width: 180px;
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            border: 1px solid #e9ecef;
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        .score-card h3 {
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            font-size: 16px;
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      </style>
    </head>
    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>非阻塞I/O模型 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
                <div class="quiz-body">
                    <div class="progress-bar">
                        <div id="progress-indicator"></div>
                    </div>
                    <div id="question-container">
                      <p id="question-text"></p>
                      <ul class="options-list" id="options-list"></ul>
                    </div>
                    <div id="result-container"></div>
                    <div id="hint-container" class="hint-container"></div>
                </div>
                <div class="quiz-footer" id="quiz-footer">
                  <button id="prev-btn" class="nav-btn">上一题</button>
                  <button id="hint-btn" class="nav-btn" style="background-color: #ffc107; color: #333; box-shadow: 0 4px 12px rgba(255,193,7,0.3);">提示</button>
                  <button id="next-btn" class="nav-btn">下一题</button>
                </div>
            </div>
          </div>
      </div>

      <script>
        const quizData = [
  {
    "question": "与传统的阻塞I/O模型相比，非阻塞I/O模型最核心的区别是什么？",
    "options": [
      "非阻塞I/O会为每个I/O请求创建一个新线程以提高效率。",
      "当I/O操作无法立即完成时，线程不会被挂起，而是立即返回，允许程序继续执行其他任务。",
      "非阻塞I/O总是能比阻塞I/O更快地完成数据传输。",
      "非阻塞I/O模型下，操作系统会缓存所有数据，直到程序请求时才一次性返回。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "根据文档描述，非阻塞I/O的核心思想是当线程请求I/O操作时，如果操作无法立即完成（例如数据未准备好），线程不会被挂起等待，而是会立即返回。这使得线程可以继续执行其他任务，从而避免了在等待I/O时造成的资源浪费，这是它与阻塞I/O最根本的区别。",
    "source": "文档中「1.1 传统阻塞I/O与非阻塞I/O的对比」部分",
    "hint": "思考一下，当数据还未准备好时，这两种I/O模型的线程会分别处于什么状态？"
  },
  {
    "question": "在非阻塞I/O模型中，当程序发起一个读请求但数据尚未准备好时，操作系统通常会如何响应？",
    "options": [
      "将线程置于休眠状态，直到数据到达后再唤醒。",
      "立即返回一个特定的错误代码（如 EAGAIN 或 EWOULDBLOCK），告知程序当前无数据可读。",
      "立即抛出一个严重异常，并中断程序的执行。",
      "返回一个空的数据包，让程序自行判断数据是否有效。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "文档明确指出，在非阻塞I/O中，如果请求的数据尚未到达，I/O操作会立即返回，并附带一个特定的错误代码或状态码，如EAGAIN或EWOULDBLOCK。这是一种预期的、非致命的“错误”，用于通知调用者“资源暂时不可用”，而不是挂起线程或终止程序。",
    "source": "文档中「2.1 I/O操作的请求」部分",
    "hint": "文档中提到了一个具体的例子，描述了在一个非阻塞的网络套接字中，如果没有数据会发生什么。"
  },
  {
    "question": "为了高效地管理多个非阻塞I/O操作（例如，同时处理多个网络连接），通常会结合使用哪种关键技术？",
    "options": [
      "多线程池技术",
      "分布式缓存技术",
      "I/O复用技术 (如 epoll, select)",
      "远程过程调用 (RPC) 框架"
    ],
    "correctAnswerIndex": 2,
    "explanation": "非阻塞I/O本身只是避免了单次I/O操作的阻塞。要高效地同时管理多个I/O句柄，就需要I/O复用技术。文档提到，通过epoll、select等机制，程序可以将多个文件描述符注册给操作系统监控，当任何一个描述符准备就绪时，操作系统会通知程序，从而让单个线程能处理多个I/O事件。",
    "source": "文档中「2.2 事件通知机制」部分",
    "hint": "想一想，如果只有一个线程，它如何知道多个网络连接中哪一个“准备好了”可以读写？"
  },
  {
    "question": "根据文档，非阻塞I/O的优势通常需要结合哪种编程模型来充分发挥？",
    "options": [
      "面向对象编程模型",
      "函数式编程模型",
      "事件驱动模型 (Event-driven model)",
      "过程式编程模型"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档强调，为了充分发挥非阻塞I/O的优势，通常需要结合事件驱动模型。在这种模型中，程序通过一个“事件循环”（Event Loop）来轮询并处理已准备好的I/O事件。这种组合使得单线程能够高效地处理大量并发连接。",
    "source": "文档中「2.3 事件循环与非阻塞I/O」部分",
    "hint": "文档中描述了一个包含“事件循环”（Event Loop）的机制，它属于哪种编程模型？"
  },
  {
    "question": "与传统的多线程I/O模型（一个连接分配一个线程）相比，使用非阻塞I/O和事件驱动模型的主要优势是什么？",
    "options": [
      "代码逻辑更简单，易于调试和维护。",
      "对所有类型的计算任务都能提供更好的性能。",
      "可以在少量线程中处理大量并发连接，显著减少线程上下文切换和资源消耗。",
      "可以完全消除网络延迟带来的影响。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档的核心优势之一是资源效率。传统模型中，大量线程会导致频繁的上下文切换和高内存消耗。而非阻塞I/O结合事件驱动模型，可以用极少的线程（甚至是单线程）来处理海量并发连接，因为线程从不因I/O而阻塞，从而大大降低了系统开销。",
    "source": "文档中「3. 非阻塞I/O与多线程的关系」部分",
    "hint": "考虑一下当有一万个并发连接时，传统模型需要什么，而非阻塞模型需要什么？"
  },
  {
    "question": "尽管非阻塞I/O在性能上有显著优势，但它也带来了一些挑战。根据文档，以下哪项是实现非阻塞I/O时面临的主要挑战之一？",
    "options": [
      "硬件成本过高，需要特殊的CPU支持。",
      "与现代操作系统不兼容。",
      "导致系统整体延迟显著增加。",
      "编程复杂度较高，需要开发者显式管理事件和处理各种状态。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "文档在“挑战与限制”部分明确指出，非阻塞I/O的编程模型比传统的同步阻塞模型更复杂。开发者需要自己处理事件循环、错误状态（如EAGAIN）、重试机制和事件调度等，这增加了编码和调试的难度。",
    "source": "文档中「5.1 编程复杂性」部分",
    "hint": "相比于“读取数据，然后处理”，非阻塞模式需要开发者考虑“现在有数据吗？没有的话我该做什么？有的话我该怎么处理？”"
  },
  {
    "question": "文档中提到了采用非阻塞I/O和事件驱动模型的典型应用范例，以下哪个是该模式的代表？",
    "options": [
      "需要大量CPU密集型计算的科学分析软件。",
      "传统的Apache Web服务器。",
      "Nginx 和 Node.js。",
      "关系型数据库内核，如MySQL。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "文档在论述非阻塞I/O与多线程关系时，明确举例说明了Node.js和Nginx等服务器是采用这种“单线程模型”（或少量线程的事件驱动模型）的典型代表，它们以高并发处理能力而闻名。",
    "source": "文档中「3. 非阻塞I/O与多线程的关系」部分",
    "hint": "文档末尾提到了一个著名的Web服务器和一个流行的JavaScript运行环境作为例子。"
  }
];
        console.log("Quiz Data:", JSON.parse(JSON.stringify(quizData))); // 添加这行用于调试，以可展开的JSON格式输出
        
        let currentQuestionIndex = 0;
        let score = 0;
        // 存储每个问题的回答状态
        const userAnswers = new Array(quizData.length).fill(null); 

        const questionTextEl = document.getElementById('question-text');
        const optionsListEl = document.getElementById('options-list');
        const resultContainerEl = document.getElementById('result-container');
        const quizContentEl = document.getElementById('quiz-content');
        const progressIndicatorEl = document.getElementById('progress-indicator');
        const prevBtn = document.getElementById('prev-btn');
        const nextBtn = document.getElementById('next-btn');
        const hintBtn = document.getElementById('hint-btn');
        const hintContainerEl = document.getElementById('hint-container');

        function loadQuestion() {
          resultContainerEl.innerHTML = '';
          optionsListEl.innerHTML = '';
          hintContainerEl.style.display = 'none'; // 隐藏提示
          
          if (currentQuestionIndex >= quizData.length) {
            showFinalScore();
            return;
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          questionTextEl.textContent = `(${currentQuestionIndex + 1}/${quizData.length}) ${currentQuestion.question}`;
          
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            li.className = 'option-item';
            li.textContent = optionText;
            li.dataset.index = index; // Store index in a data attribute
            // 如果这道题已经回答过，恢复状态
            if (userAnswers[currentQuestionIndex] !== null) {
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                    li.classList.add('selected');
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            optionsListEl.appendChild(li);
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          // 如果已经回答过，直接显示结果
          if (userAnswers[currentQuestionIndex] !== null) {
              const isCorrect = userAnswers[currentQuestionIndex] === currentQuestion.correctAnswerIndex;
              showResult(isCorrect, currentQuestion);
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          updateNavigationButtons();
          updateProgress();
        }

        function selectOption(optionIndex) {
            userAnswers[currentQuestionIndex] = optionIndex;
            const currentQuestion = quizData[currentQuestionIndex];
            const isCorrect = optionIndex === currentQuestion.correctAnswerIndex;

            // 重新计算分数
            score = userAnswers.reduce((acc, answer, index) => {
                return answer === quizData[index].correctAnswerIndex ? acc + 1 : acc;
            }, 0);

            showResult(isCorrect, currentQuestion);
            updateNavigationButtons();
        }
        
        function updateProgress() {
            const answeredQuestions = userAnswers.filter(answer => answer !== null).length;
            const progressPercentage = (answeredQuestions / quizData.length) * 100;
            progressIndicatorEl.style.width = `${progressPercentage}%`;
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        function updateNavigationButtons() {
            prevBtn.style.display = 'block';
            nextBtn.style.display = 'block';
            hintBtn.style.display = 'block'; // 显示提示按钮

            prevBtn.disabled = currentQuestionIndex === 0;
            nextBtn.disabled = false; // 最后一题时，下一题按钮不禁用，而是用于显示报告
            nextBtn.textContent = (currentQuestionIndex === quizData.length - 1) ? '查看报告' : '下一题';
            
            // 如果当前问题没有提示，则禁用提示按钮并隐藏提示内容
            if (!quizData[currentQuestionIndex].hint) {
                hintBtn.disabled = true;
                hintContainerEl.style.display = 'none';
                hintContainerEl.textContent = ''; // 清除旧的提示内容
            } else {
                hintBtn.disabled = false;
            }
        }

        function showResult(isCorrect, questionData) {
            resultContainerEl.innerHTML = ''; // 清空之前的结果
            const resultBox = document.createElement('div');
            resultBox.className = `result-box ${isCorrect ? 'correct' : 'incorrect'}`;
            
            let html = `<h3>${isCorrect ? '回答正确！' : '回答错误'}</h3>`;
            if (!isCorrect) {
                html += `<p><strong>正确答案是：</strong> ${questionData.options[questionData.correctAnswerIndex]}</p>`;
            }
            html += `<div class="explanation-text">${questionData.explanation}</div>`;
            html += `<div class="source-text">来源: ${questionData.source}</div>`;
            
            resultBox.innerHTML = html;
            resultContainerEl.appendChild(resultBox);

            // 禁用所有选项的点击事件，并高亮正确/错误答案
            Array.from(optionsListEl.children).forEach((child, index) => {
                child.style.pointerEvents = 'none';
                // 高亮正确答案
                if (index === questionData.correctAnswerIndex) {
                    child.classList.add('correct'); // 需要添加CSS样式
                    child.style.backgroundColor = '#d4edda';
                    child.style.borderColor = '#c3e6cb';
                }
                // 如果选错了，高亮错误选项
                if (!isCorrect && index === userAnswers[currentQuestionIndex]) {
                    child.classList.add('incorrect'); // 需要添加CSS样式
                    child.style.backgroundColor = '#f8d7da';
                    child.style.borderColor = '#f5c6cb';
                }
            });
        }

        function goToNextQuestion() {
            if (currentQuestionIndex < quizData.length - 1) {
                currentQuestionIndex++;
                loadQuestion();
            } else {
                showFinalScore();
            }
        }

        function goToPreviousQuestion() {
            if (currentQuestionIndex > 0) {
                currentQuestionIndex--;
                loadQuestion();
            }
        }
        
        function showHint() {
            const currentQuestion = quizData[currentQuestionIndex];
            if (currentQuestion.hint) {
                hintContainerEl.textContent = currentQuestion.hint;
                hintContainerEl.style.display = 'block';
            } else {
                hintContainerEl.style.display = 'none';
            }
        }

        function showFinalScore() {
            document.querySelector('.quiz-body').style.display = 'none';
            document.getElementById('quiz-footer').style.display = 'none';

            const correctCount = score;
            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

            const finalScoreHtml =
                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  